The proposed studies are designed to increase our understanding of the interaction of steroid hormones and catecholamines with vascular tissue. Experiments will be carried out with rats in vivo and with rat aortic smooth muscle cells grown in tissue culture. The influence of these hormones on intracellular pools of cyclic AMP and the activity of adenylate cyclase and phosphodiesterase in vascular smooth muscle will be determined. The mechanism by which glucocorticoids and mineralocorticoids potentiate catecholamine-stimulated increases in cyclic AMP will be explored. In related experiments, the effect of steroid hormones and catecholamines on the phosphorylation of vascular proteins will also be examined. Emphasis will be placed on proteins though to regulate smooth muscle contraction. These studies will be correlated with the kinetics of cyclic AMP formation. Parallel experiments will be carried out with rats that are sensitive and resistant to mineralocorticoid hypertension. This genetic difference in sensitivity will be used to explore the function of steroid hormones in vascular tissue; their interaction with adrenergic agonists and their possible role in blood pressure regulation.